using System;
using System.Net;
using System.Net.Sockets;
using System.Text;

namespace Demo
{
    class Program
    {
        static void Main()
        {
            int receivedDataLength;
            byte[] data = new byte[1024];
            IPEndPoint ip = new IPEndPoint(IPAddress.Any, 24242);

            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

            socket.Bind(ip);

            IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0);
            EndPoint Remote = (EndPoint)(sender);

            while (true)
            {
                data = new byte[1024];
                receivedDataLength = socket.ReceiveFrom(data, ref Remote);

                Console.WriteLine(Encoding.ASCII.GetString(data, 0, receivedDataLength));
                socket.SendTo(data, receivedDataLength, SocketFlags.None, Remote);
            }
        }
    }
}